It is known that organic and polymeric materials with large delocalized .pi.-electron systems can exhibit nonlinear optical response, which in many cases is a much larger response than by inorganic substrates.
In addition, the properties of organic and polymeric materials can be varied to optimize other desirable properties, such as mechanical and thermoxidative stability and high laser damage threshold, with preservation of the electronic interactions responsible for nonlinear optical effects.
Thin films of organic or polymeric materials with large second order nonlinearities in combination with silicon-based electronic circuitry have potential as systems for laser modulation and deflection, information control in optical circuitry, and the like.
Other novel processes occurring through third order nonlinearity such as degenerate four-wave mixing, whereby real-time processing of optical fields occurs, have potential utility in such diverse fields as optical communications and integrated circuit fabrication.
Of particular importance for conjugated organic systems is the fact that the origin of the nonlinear effects is the polarization of the .pi.-electron cloud as opposed to displacement or rearrangement of nuclear coordinates found in inorganic materials.
Nonlinear optical properties of organic and polymeric materials was the subject of a symposium sponsored by the ACS division of Polymer Chemistry at the 18th meeting of the American Chemical Society, September 1982. Papers presented at the meeting are published in ACS Symposium Series 233, American Chemical Society, Washington, D.C. 1983.
Of more specific interest with respect to the present invention embodiments is prior art relating to tetracyanoquinodimethane compounds, such as U.S. Pat. Nos. 3,115,506; 3,226,389; 3,408,367; 3,681,353; 3,687,987; 3,953,874; 3,981,848; 4,046,563; 4,229,364; 4,478,751; and 4,546,059.
Also of interest are the photoconducting polyamides described in U.S. Pat. No. 3,554,743, which are characterized by a recurring unit of the formula: ##STR2## where R.sub.1 is hydrogen or lower alkyl, R.sub.2 and R.sub.3 are divalent hydrocarbon radicals, at least one of which is a phenyl or polyphenyl divalent radical.
The above-recited publications and patents are incorporated herein by reference.
There is continuing research effort to develop new nonlinear optical organic systems for prospective novel phenomena and devices adapted for laser frequency conversion, information control in optical circuitry, light valves and optical switches. The potential utility of organic materials with large second order and third order nonlinearities for very high frequency application contrasts with the bandwidth limitations of conventional inorganic electrooptic materials.
Accordingly, it is an object of this invention to provide organic compositions which are characterized by a large delocalized conjugated .pi.-electron system which can exhibit nonlinear optical response.
It is another object of this invention to provide a novel class of polymers which is characterized by a recurring charge asymmetric quinodimethane conjugated structure.
It is another object of this invention to provide high performance nonlinear optical media.
It is a further object of this invention to provide an electrooptic light modulator device with a transparent polymeric nonlinear optical component.
Other objects and advantages of the present invention shall become apparent from the accompanying description and examples.